In existing robot systems, an apparatus is configured so that a hand driving output signal is corrected using a touch sensor, a position sensor, a force sensor, or a deviation sensor of a hand section. Whether or not an object is held is determined based on outputs of the individual sensors, thereby achieving reliable holding (e.g., refer to Patent Document 1).
Furthermore, in order to recognize the position of an object to be held, the posture and position of a hand at the time of holding the object is simulated using image information from a plurality of cameras, the relative relationship between the object to be held and the hand is evaluated based on certain indices, and an optimum posture and position of the hand is selected based on the results of evaluation of all the relationships (e.g., refer to Patent Document 2).
FIG. 19 is an overall configuration diagram of a robot that uses the holding method according to Patent Document 1 describing the existing art.
Referring to FIG. 19, 101 denotes a robot hand, 102 denotes a sensor signal processing section, 103 denotes a control calculator, 104 denotes a driving section, 105 denotes a force sensor, 106 denotes a position sensor, 107 denotes a touch sensor, and 108 denotes a deviation sensor.
Now, the overall configuration of the robot that uses the holding method according to Patent Document 1 will be described with reference to FIG. 19.
The sensor signal processing section 102 converts signals from the four types of sensors provided on the robot hand 101, i.e., the force sensor 105, the position sensor 106, the touch sensor 107, and the deviation sensor 108, into signals that can be processed by the control calculator 103, and sends the signals to the control calculator 103. Upon receiving the signals regarding the status of holding an object from the sensor signal processing section 102, the control calculator 103 corrects signals for controlling movement regarding holding of the object by the robot hand 101. The driving section 104 converts the control signals from the control calculator 103 into power with which the robot hand 101 can be driven, and sends the power to the driving section 104 of the robot hand 101, i.e., to the driving mechanism and motor. Furthermore, the driving section 104 supplies electric power to the four types of sensors, i.e., the force sensor 105, the position sensor 106, the touch sensor 107, and the deviation sensor 108. At least two force sensors 105 are provided, which measure reaction forces received from a held object at the time of holding. The position sensor 106 measures the holding space of the object held. At least two touch sensors 107 are provided, which determine the status of touching with the object to be held. The deviation sensor 108 detects a deviation of the object to be held.
FIG. 20 is a control block diagram of the robot system according to Patent Document 1 describing existing art.
In FIG. 20, 109 denotes target deformation ratio setting, 110 denotes reaction force target value setting, 111 denotes deformation ratio determination, 112 denotes reaction force determination, A denotes reaction force target value, B denotes target deformation ratio, C denotes status of touching, D denotes hand position, and E denotes reaction force. Reference numerals that are the same as those in FIG. 19 denote the same components as those in FIG. 19, and description thereof will be omitted.
Now, an operation of the robot system according to Patent Document 1 will be described with reference to FIG. 20.
By feedback of signals from the sensor signal processing section 102 to the control calculator 103, it is determined whether holding has been executed properly. If a deviation of the object to be held is detected by the touch sensor 107 or the deviation sensor 108, the target deformation ratio setting 109 and the reaction force target value setting are performed again, and position control and force control are executed again.
FIG. 21 is a flowchart for explaining an operation of the robot system according to Patent Document 2 describing existing art.
First, terms used in the flowchart in FIG. 21 will be described.
A “sum S” is obtained by finding, regarding edges in a model of a robot hand in a case where models of a robot and individual components are projected onto a camera screen, portions that are viewable without being hidden by individual surfaces in the model of parts other than the robot hand and models of the individual components of the robot, converting the lengths of the portions into lengths in a three-dimensional space, and summing up values of the converted lengths.
An “evaluation value P” can be expressed as P=S/M, where M is a sum obtained by converting the lengths of all the edges in the model of the robot hand into lengths in a three dimensional space and summing up the values of the converted lengths.
Next, individual steps in a procedure of processing by the robot system described in Patent Document 2 describing existing art will be described in detail with reference to FIG. 21.
In step ST100, based on an image captured by a camera, a case where a robot and individual components are projected onto a screen is simulated. Next, in step ST200, the sum S is calculated and the evaluation value P is obtained. Then, in step ST300, it is checked whether step ST200 has been executed for all the holding positions and/or postures. In step ST400, the evaluation values P of the individual holding positions and/or postures are compared. Then, in step ST500, a holding position and/or posture with a maximum value of the evaluation value P is selected.
As described above, in robot systems according to existing arts, an object is held using information of either a sensor or a camera.    Patent Document 1: Japanese Unexamined Utility Model Application Publication No. 5-31887 (page 2 and FIGS. 1 and 3)    Patent Document 2: Japanese Unexamined Patent Application Publication No. 5-150835 (pages 2 to 4 and FIG. 1)